Hydraulic pressure transformer

ABSTRACT

A hydraulic pressure transformer for the delivery of liquid under high and low pressure comprising a first bore for control purposes with three pistons on a common piston rod and at least two concentric bores of different cross sections with two working pistons of different cross sections connected by a common piston rod. The bores are interconnected by passages to effect pressure transformation of the liquid.

States atent m1 0 Kitten 3,720,484 Kirshsieper 51March 13, 1973 [54]HYDRAULIC PRESSURE 2,539,292 1/1951 Anderson ..417/225 SFORMER 2,826,1493/1958 Wrigley 417/225 2,864,313 12/1958 Dawson ....417/225 [76]Inventor: Walter Kirshsieper, Urechmatt 121, 3,349,995 10/1967 Sheesley..417/225 5445 Eggenwil, Switzerland Filed: March 1971 PrzmaryExammer-Carlton R. Croyle Appl. No.: 120,285

Foreign Application Priority Data March 4, 1970 Switzerland ..3l42/70References Cited UNITED STATES PATENTS 12/1874 Loretz ..417/225Assistant Examiner-Richard Sher Att0rneyArnold Robinson [57] ABSTRACT Ahydraulic pressure transformer for the delivery of liquid under high andlow pressure comprising a first bore for control purposes with threepistons on a common piston rod and at least two concentric bores ofdifferent cross sections with two working pistons of different crosssections connected by a common piston rod. The bores are interconnectedby passages to effect pressure transformation of the liquid.

1 Claim, 1 Drawing Figure HYDRAULIC PRESSURE TRANSFORMER This inventionrelates to a hydraulic pressure transformer for raising the pressure ofa working fluid and able to deliver the same at low pressure as well ashigh pressure.

There are hydraulically powered machines, such as stamping anddeep-drawing presses, which require a high pressure in the hydraulicdrive for the working stroke and a low pressure for tool withdrawalpossibly with rapid travel.

The pressure transformer according to the invention has for its objectto generate both these pressures.

The hydraulic pressure transformer of this invention comprises a housingwith passages for the inlet and outlet of a liquid working medium underpressure and for delivery of same at low-pressure as well as athigh-pressure; a first bore for a control slide with three separatepistons arranged on a common piston rod at intervals from each other,and at least two concentric bores for at least two working pistons ofdifferent cross sections connected with each other; a first passage intothe space between the first and second or second and third pistons ofthe control slide, for supplying working fluid, a first duct from saidintermediate space to the free end of the first working pistons; asecond passage from the space between the first and second pistons ofthe control slide to the outside for delivering the working piston intothe space between the first and second pistons of the control slide, athird duct leading from the space at the free end of the third piston ofthe control slide into the bore for the second working piston, a fourthduct leading from the space between the working pistons to the spacebehind the free end of the first piston of the control slide, and thirdpassage for delivery of the working fluid under increased pressurethrough the bore for the first working piston, the first duct and thefirst bore to the outside, whereby the second and third pistons of thecontrol slide alternately open and close the second and third passagesupon displacement of the control slide, and the second working pistonuncovers or blocks the opening of the third duct in its bore and thefirst piston uncovers or blocks the opening of the fourth duct in itsbores.

The accompanying drawing shows a diagrammatic sectional view of apreferred form of embodiment of the hydraulic pressure transformer.

In said annexed drawing the hydraulic pressure transformer showncomprises a housing 1 with a bore 2, in which pistons 4, 5 and 6 linkedwith a piston rod 3 are displaceably fitted. Said pistons act as controlelements for the pressure transformer.

A bore 7 in housing 1 has displaceably arranged therein a low-pressurepiston 8, and a bore 9 concentric with bore 7 a high-pressure piston 10.Pistons 8 and 10 are connected by a piston rod 1 1.

Three passages 12, 13 and 14 lead out from the bore 2. A duct 15connects the bore 9 with the space to the left of piston 4 in the bore2. The space to the right of piston 6 communicates via a duct 16 withbore 7, between pistons 8 and 10. The opposite ends of bores 7 and 9communicate via ducts l7 and 18 with the spaces of bore 2 betweenpistons 4, .5 and 5, 6 respectively. Finally from the spaces of bores 7and 9 a duct 19 leads out between the pistons 8 and l0.

The pressure transformer described is connected through the passage 12with a source supplying liquid (working fluid) under low pressure, say,from a lowpressure pump.

In the starting position shown, the working fluid enters the bore 2,whence it passes via duct 18 into the space behind the high-pressurepiston 10 on the right. The same is forced (to the left in the drawing)by the working fluid, moving the low-pressure piston 8 in the samedirection through piston rod 11. The fluid remaining in bore 7 isejected through duct 17 and passage 13 by this movement of piston 8.Passage 14 is blocked by piston 6.

As soon as the piston 10 uncovers the duct 15 leadinginto bore 9, theworking fluid flows through duct 15 into the space on the left behindpiston 4, pushing same to the right together with pistons 5 and 6. Thefluid on the right in the space behind piston 6 passes through duct 16into bore 7. A duct 19 allows leakage fluid to escape outside.

Upon displacement of pistons 4, 5 and 6, piston 4 blocks the passage 13and piston 6 opens the way for the fluid in bore 9 to the passage 14.The working fluid then flows from passage 12 through duct 17 into thespace on the left behind piston 8, moving same to the right togetherwith piston 10. As a result, a pressure is established in bore 9 asdetermined by the pressure of the low-pressure pump and the ratiobetween the cross sections of pistons 8 and 10. The working fluid nowunder higher pressure is forced to the working point through passage 14.

As soon as this movement of piston 8 uncovers the opening of duct 16into bore 7, the working fluid passes through duct 16 into the space onthe right behind piston 6, pushing same to the left together withpistons 4 and 5. The fluid in the space to the left of piston 4 runs offthrough duct 15 and duct 19.

The parts of the pressure transformer are now again back in theirstarting positions according to the drawing, and the aforedescribedcycle is repeated.

ln this way the pressure transformer allows consecutive pressure pulsesto be delivered, with alternately higher and lower pressure.

Thus for example on hydraulically powered deepdrawing and stampingpresses the high-pressure pulse from the passage 14 can be used for theworking stroke of the press, while the rapid return of the press tool isbrought about with the low-pressure pulse from passage 13, or else acontrol valve may be needed in advance of the pressure transformer toswitch it over when the maximum pressure of the low-pressure pump isreached.

Alternatively a number of pistons 8 and 10 may be arranged in parallelto reduce the pulsating pressure delivered.

The pressure transformer starts in any position.

By arranging a pressure limiting means, such as a spring, betweenpistons 8 and 10, and making these displaceable in relation to eachother, a pressure limitation may be obtained. With the maximumadmissible pressure reached by the high-pressure piston, piston 10 comesto a stop, whilst the low-pressure piston 8 will be displaced furtheragainst the action of the limiting means, until the opening of duct 16isvuncovered thus causing the pressure transformer to be switched over.

Piston 10 then returns to its particular starting position. At the nextreversal of pistons 4, 5 and 6 (control pistons) the high-pressurepiston 10 only covers the pressure drop caused by the leakage losses. Aslong as working fluid is required at the same pressure, this mode ofoperation will be repeated by the pressure transformer thus designed.With pressure relieved below the switch-over pressure, the pressuretransformer ceases to operate.

What I claim is:

l. A hydraulic pressure transformer, having a housing with passages forthe inlet ofa liquid working medium under pressure and for delivery ofsame at low pressure as well as at high pressure; a first bore having acontrol slide therein with three separate pistons arranged on a commonpiston rod at intervals from each other, and at least two connectingconcentric bores of different cross sections with at least one workingpiston in each said concentric bore, said working pistons each beingadapted to make a sliding engagement with its respective bore, saidworking pistons being connected with each other by a common piston rodof cross section smaller than that of either of said bores; a firstpassage opening alternatively into the space between the first andsecond pistons and between the second and third pistons of the controlslide, for supplying working fluid, a first duct connecting said spacebetween the second and third piston to the space behind the free end ofthe first working piston; a second passage connecting the space betweenthe first and second pistons of the control slide to the outside fordelivering the working fluid under low pressure, a second duct extendingfrom the free end of the second working piston into the space betweenthe first and second pistons of the control slide, a third duct leadingfrom the space at the free end of the third piston of the control slideinto the bore for the second working piston, a fourth duct leading fromthe space behind the free end of the first piston of the control slideinto the bore for the first working piston, a third passage for deliveryof the working fluid under increase pressure from the bore for the firstworking piston through the first duct and the first bore to the outside,and a vent passage connecting the said concentric bores with the outsideand having its opening to the bores located between the openings of saidthird and fourth ducts, whereby the first and third pistons of thecontrol slide alternately open and close the second and third passagesrespectively upon displacement of the control slide, and the secondworking piston alternately communicates the opening of the third duct inits bore with the space behind the free end of the second working pistonand the opening of the vent passage; and the first working pistonalternately communicates the opening of the fourth duct in its bore withthe space behind the free end of the first working piston and theopening of the vent passage.

1. A hydraulic pRessure transformer, having a housing with passages forthe inlet of a liquid working medium under pressure and for delivery ofsame at low pressure as well as at high pressure; a first bore having acontrol slide therein with three separate pistons arranged on a commonpiston rod at intervals from each other, and at least two connectingconcentric bores of different cross sections with at least one workingpiston in each said concentric bore, said working pistons each beingadapted to make a sliding engagement with its respective bore, saidworking pistons being connected with each other by a common piston rodof cross section smaller than that of either of said bores; a firstpassage opening alternatively into the space between the first andsecond pistons and between the second and third pistons of the controlslide, for supplying working fluid, a first duct connecting said spacebetween the second and third piston to the space behind the free end ofthe first working piston; a second passage connecting the space betweenthe first and second pistons of the control slide to the outside fordelivering the working fluid under low pressure, a second duct extendingfrom the free end of the second working piston into the space betweenthe first and second pistons of the control slide, a third duct leadingfrom the space at the free end of the third piston of the control slideinto the bore for the second working piston, a fourth duct leading fromthe space behind the free end of the first piston of the control slideinto the bore for the first working piston, a third passage for deliveryof the working fluid under increase pressure from the bore for the firstworking piston through the first duct and the first bore to the outside,and a vent passage connecting the said concentric bores with the outsideand having its opening to the bores located between the openings of saidthird and fourth ducts, whereby the first and third pistons of thecontrol slide alternately open and close the second and third passagesrespectively upon displacement of the control slide, and the secondworking piston alternately communicates the opening of the third duct inits bore with the space behind the free end of the second working pistonand the opening of the vent passage; and the first working pistonalternately communicates the opening of the fourth duct in its bore withthe space behind the free end of the first working piston and theopening of the vent passage.